Teen e-cigarette use declined this year, according to results from the National Youth Tobacco Survey, marking a positive trend that health officials say still leaves the number of users too high.

In 2020, 19.6% of high-school students and 4.7% of middle-school students said they vaped, according to the survey co-sponsored by the Centers for Disease Control and Prevention and the Food and Drug Administration. Those numbers represent declines from last year’s highs, when more than a quarter of high-school students and about 1 out of 10 middle-school students reported using e-cigarettes.

“Although the decline in e-cigarette use among our nation’s youth is a notable public health achievement, our work is far from over,” CDC Director Robert Redfield said in a statement. About 3.6 million youths reported using e-cigarettes within the prior 30 days, down from 5.4 million in the 2019 survey.

The influential survey has shaped the debate around e-cigarettes in recent years. While billed as a possibly less harmful alternative for the millions of adults who smoke cigarettes, the high rate of teen vaping has cast doubt on whether the products should be available at all.

The FDA will soon determine which e-cigarettes can stay on the US market and which must come off. Wednesday is the deadline for applications.